Package: Mobs Monster
As first pointed out by Tim7, some textures seem to be upscaled MC textures.
Might be worth double checking if the texture pack you used for them allows licensing like this...
Transformative is only a fair use defense in court, so yes mobs_tree_monster3.png needs to be changed. I think the upscaled tree texture comes from the Faithful resource pack.
In addition there's also mobs_cobweb.png which is literally just the old Minecraft cobweb texture and mobs_tree_monster6.png which looks awfully close to the texturing of the Creeper in Faithful.